Can you make an upgrade of hilt and use it even if its only a generic double bladed hilt?

As long as said double bladed saber is customizable then yes. Like I said before, the hilt modifications that artifice make are used in any saber style. They won't change the appearance of the saber at all, they're just there to upgrade the damage and add stats to customizable sabers. You will know if your saber is moddable because it will have "slots" listed, with various mods in them or say Open.
Saber slots include:
Crystal - Changes color and add a stat
Hilt - Changes damage and adds primary stats
Modification - Adds primary and secondary stats
Enhancement - Adds secondary stats